In many semiconductor components, interconnects or electrodes made of polysilicon are patterned on a top side. For this purpose, a polysilicon layer is applied over the whole area, and subsequently patterned using a mask, in particular by means of a photoresist and photolithography. In the region of the mask openings, the polysilicon is removed by etching, which may be effected for example by means of RIE (reactive ion etching). The gate electrodes of transistor structures which are also used for memory cells of semiconductor memory components are produced in this way. EEPROM components are provided so-called floating gate electrodes, which are arranged between a control gate electrode above the channel region of the transistor and are electrically insulated all around. Charge carriers are accumulated on said floating gate electrodes during programming.
In the customary production process, such electrodes in polysilicon are produced with rather sharp, at least approximately right-angled edges. What is disadvantageous in this case is that the electric field assumes particularly high values at edges and points of conductor surfaces, with the result that conditions are present there for a breakdown and a discharge through the electrically insulating material. This fact adversely affects a multiplicity of applications of the semiconductor components. Therefore, it is desirable to have available a simple process by which the electrode structures can be formed without excessively sharp edges or corners. One possibility for achieving this is reoxidation of the polysilicon surfaces at a high oxidation temperature. However, rounded corners can be produced by this process only as long as the dimensions of the structures produced lie above a specific limit. This is because the temperatures that can be employed are limited depending on the structure width, so that in the case of very small structures, rounded edges cannot be produced by means of the oxidation steps and in fact that sharpness of the edges becomes even more greatly pronounced.
The customary mask technique for patterning semiconductor layers uses photolithography, by means of which an applied photoresist is exposed in a manner corresponding to the structures to be produced and is then developed. Depending on the type of photoresist, the exposed portions or the unexposed portions are removed after development. In order to improve the optical conditions during photolithography, an antireflection layer is provided below the photoresist. The antireflection layers are usually very thin in relation to the resist layers. One commercially available material used as BARC (bottom antireflective coating) is WIDE-15 from the company Brewer Science.